There exist a wide variety of applications in the field of electronics, robotics, science, engineering and art where an implement of some kind must be positioned with respect to a fiducial point or other reference in a mechanical system. For convenience and definiteness, this specification will be written in terms of a positioner useful for accurately positioning instruments used for the testing of integrated circuits, but it is in no way intended that this invention should be limited to the testing field.
In testing an integrated circuit, it is required to bring an electrically conductive probe near to or in contact with an electrically conductive path of the circuit under test. In modern-day integrated circuits, the electrically conductive parts of integrated circuits are often smaller than one micrometer in extent. Therefore it is required that a test probe must be positioned to an accuracy that is better than one micrometer. Prior art micropositioners either are unable to respond with the required precision or are very expensive to construct and are inconveniently large in physical size, making them difficult to use in many important applications.
Prior art micropositioners have been generally of three forms: the most common form consisting of three precision screws oriented in three directions of motion (up and down, right and left, forward and back) that each drive a precision machined sliding member held captive inside a precision machined groove (e.g., see U.S. Pat. No. 3,517,904, June 30, 1970). Such an apparatus is expensive to construct because of the precision machining required. In addition, the screw must be manipulated by the operator's hand and the force of the hand on the positioner produces random, undesirable movements due to the limited mechanical rigidity of the mounting that holds the positioner. Motorized drivers to adjust the positioning screws can be used to eliminate the hand induced movement but the consequence is an increase in cost and size of the micropositioner.
The joystick style micropositioner available from Signatone Corp., 2687 Enochs Street, Santa Clara, Calif. 95051, although used extensively from 1950 to about 1970, is no longer in common use today because of the limited travel and because the precision is less than required.
A piezoelectric linear driver or inchworm positioner mechanism (e.g.,, see U.S. Pat. No. 4,525,852, June, 1985), although giving good precision of movement, is very expensive to construct and is too easily damaged in normal laboratory or production use.
It is therefore desirable to provide an apparatus that is both relatively inexpensive to construct and provides the precise movement required.